JP2006257383A - Lubricant composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant composition which has a low frictional property to enable its use for a long time under severe conditions and has excellent wear resistance. <P>SOLUTION: This lubricant composition for existing and receiving shears between two surfaces moved at mutually different circumferential speeds is characterized by comprising (a) at least one organic compound which has a mesogenic structure capable of forming a liquid crystal phase in the molecule and a viscosity pressure coefficient of ≤20 GPa<SP>-1</SP>at 40°C, and expresses the minimum traction coefficient value with the increase of pressure under a pressure of ≥10 MPa, (b) a lubricating base oil, and (c) at least one viscosity index-improving agent and/or (d) at least one antioxidant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lubricant composition interposed on sliding surfaces of various machine elements that frictionally slide, and particularly to a lubricant composition that is excellent in lubricity and durability to various interfaces under elastohydrodynamic lubrication conditions. .

Tribology, according to the OECD terminology, is “Science and technology related to surfaces that interact with each other, and related problems and practical applications”.
Tribology is a basic technology common to all industrial machines and devices that operate in the world, and its industrial fields include transportation, electronics / precision machinery, industrial machinery / chemical machinery, machinery / component manufacturing, space development, biological / health and It is very diverse with home appliances.
However, so-called lubricating oil reduces the friction coefficient of sliding contact parts such as bearings and engines, reduces wear, and the main interface material that extends the mechanical life is mostly steel.
The current lubricant technology has a mission to achieve both a low coefficient of friction and wear resistance, but at start-up and at low loads, a low coefficient of friction is obtained by a low viscosity base oil, and at high loads, a low coefficient of friction is obtained by a boundary lubricant film. On the other hand, functional sharing has been performed in which wear resistance (which is impaired due to the low viscosity base oil) is compensated by boundary lubrication film technology based on the formation of a reactive film on iron.

However, the situation so far has recently changed dramatically.
For one thing, the current boundary lubrication film technology (all ironically) is made up of environmentally hazardous substances (sulfur, phosphorus, halogens) or substances of concern (heavy metals), ELV (End of Life Vehicles), WEEE ( Next to the technology of Waste Electric and Electronic Equipment (Electrical and Electronic Equipment), RoHS (Restriction of the use of certified Hazardous Subsectors in electrical and electronic environment) This is because it is required.
Another factor is that high-hardness engineering plastics, ceramics with high processing accuracy, and various surface processing technologies have emerged. Materials that have properties not found in steel, light weight, high hardness, corrosion resistance, etc. This is because wear resistance lubrication technology suitable for the material has come to be demanded.
In addition, the “Study on Creation of Green Tribo Materials” report by the Japan Science and Technology Strategy Promotion Organization (JCII) includes a reduction in maintenance costs and parts replacement costs, a reduction in spillage losses caused by failures, and an increase in the lifespan of equipment investment. It has been pointed out that the reduction accounted for 82% of the economic effect of 8.63 trillion yen due to the improvement of tribology in FY2002. This suggests that new lubrication technology with higher performance is necessary. It is a lubricating oil that can provide a boundary lubricating film that can further enhance the performance of the lubricating action as a fluid and minimize damage even under extreme conditions.

However, all of the conventional boundary lubrication film technologies are based on reactivity to steel, and the “new” elements that react to such strong steel and are harmless have both high reactivity and safety at the same time. It is not easy to develop an alternative technology because it is required.
However, without the wear resistance technology, the low-viscosity base oil technology cannot be used, and various additive technologies cannot be used. Of course, it is also non-reactive at other interfaces where high hardness is expected (inorganic coatings other than iron such as ceramics, engineering plastics, and diamond-like carbon), so the same development of wear resistance functions. I can't expect.
From the above discussion, what is currently required is low friction and wear resistance composed of environmentally friendly elements under high pressure and high shear conditions where the steel interface is distorted (elastically deformed). It is an excellent “new” lubricant film formation technology.

Environments that do not follow Newton's viscosity law, such as phase transitions under high pressure, adsorbed molecular films near the interface, and oriented molecular films, polar molecules that are not aliphatic compounds, and discoidal molecules that are not string-like molecules (anisotropic) In current tribology, it is not easy to predict the behavior at the interface from its physical properties.
Furthermore, the fact that the orientation of molecules is greatly influenced by the properties of the interface is well known by the technology of alignment films for liquid crystals developed for liquid crystal displays. Therefore, we have to say that it is difficult to make reliable predictions with conventional knowledge.

  Originally, the basic role of lubricants is to achieve both low friction and wear resistance, but organic materials that can achieve both low friction in extreme pressure shear fields and wear resistance due to the formation of a strong oil film. Is not obtained with aliphatic compounds. The behavior of other organic compound materials such as polar organic compounds having a heterocyclic ring, liquid crystalline compounds that are self-organized, and organic compounds that are not liquid crystalline but have large structural anisotropy Has never been studied in detail from a tribological perspective.

  As shown in Patent Document 1, by combining a soft base oil (synthetic base oil, mineral base oil, etc.) and a viscosity index improver that compensates for its too soft defect, both low friction and wear resistance can be achieved. A lubricating oil composition for an internal combustion engine is provided. However, there is no description about the durability improvement of the viscosity index improver.

  Patent Document 2 provides a lubricating oil composition that exhibits a low coefficient of friction containing a discotic compound having a triazine structure. Moreover, it is described that SUJ-2 steel is excellent in wear resistance. In particular, the molecular orientation is easily imagined that the influence of the interface is significant because the technology of the liquid crystal alignment film is extremely important in the liquid crystal display, but there is no interdisciplinary research on this point. It is interesting that Patent Document 2 suggests that the low friction coefficient may be due to the orientation effect of molecules, but there is no suggestion regarding wear resistance and no description of the action at other interfaces. Moreover, there is no description about the durability improvement of a viscosity index improver.

  Patent Document 3 provides a low-friction fluid that can further reduce the frictional resistance of a sliding portion under fluid lubrication conditions and elastohydrodynamic lubrication conditions, and an engine oil including the fluid. It is described that the low friction fluid can provide a low friction resistance under both fluid lubrication and elastohydrodynamic lubrication. However, it suggests that the viscosity-pressure coefficient is relatively small, which is a technique different from the technique of the present invention that provides a characteristic low frictional resistance under elastohydrodynamic lubrication. There is also no description of molecular orientation and no other interface wear resistance. Moreover, there is no description about the durability improvement of a viscosity index improver.

  That is, it is true that the low friction fluid disclosed in the patent documents so far actually gives a low friction value in the range shown in the examples at the steel interface, but regarding compatibility with wear resistance, Although it is disclosed that the compound disclosed in Patent Document 2 has the performance in steel, no description on the interface of other materials other than steel is found. Moreover, there is no description about the durability improvement of a viscosity index improver. However, from the viewpoints of energy saving, prevention of global warming, and environmental protection, there are severe performance requirements such as improvement in fuel consumption, long life and suitability for reuse of machine elements including lubricants. Therefore, lubricant technology and machine element systems that can achieve both a low friction coefficient and wear resistance in all interface member systems, and that can extend the service life, are positioned as extremely important technologies in future developments. I understand.

  By the way, in the world of friction and lubrication between two surfaces, the friction force F is generally expressed by the product of the load W applied thereto and the friction coefficient μ reflecting the properties of the friction interface. In so-called fluid lubrication, in which oil film is present and shearing is applied, the friction that is equivalent to the coefficient of friction μ is obtained especially in the case where two cylinders having different peripheral speeds of the bearing, which are the most common as a friction machine element, make rolling / sliding contact. A coefficient φ is defined. The traction coefficient greatly depends on the nature of the intervening oil film, in addition to the shape of the contact surface, the relative speed between the two surfaces and the load. The properties of this oil film are theoretically expressed by the Navier-Stokes equation describing the motion of a viscous fluid. Reynolds applies this to narrow gap flows, and the basis of today's fluid lubrication theory. The Reynolds equation was derived, and it was shown that the pressure, wall speed, density, viscosity and thickness of the gap were determined.

If a mechanical element that needs to reduce friction and wear is determined by the lubricant, its pressure and wall speed can be controlled. The density and viscosity of the organic compound liquid as the lubricant vary depending on the pressure and temperature, but in particular, the viscosity varies much more than the density. Many bearings are used in automobiles and various manufacturing machines, but it is not uncommon that a pressure of several tons / cm ² (= several hundred MPa) is applied to the load because the contact portion with respect to the load is small. Therefore, the physical properties of viscosity at high pressure are important factors affecting the traction coefficient φ.

The viscosity in the high pressure state is expressed as a function of pressure according to the BARUS equation η = η ₀ exp (αP) (where η ₀ represents the viscosity at normal pressure). As shown in Table 1 of Non-Patent Document 1, in a normal viscous organic compound liquid, the product of the viscosity pressure coefficient α and the pressure P is 1 or more. Increase. In Non-Patent Document 2, this phenomenon is called a piezoviscous effect. In general lubricating oil, the effect of pressure exceeds 100 MPa, and the pressure rise is accelerated by the synergistic action of the wedge action and the piezoviscous effect. . Further, it is described that, if there is no elastic deformation, the oil film pressure rises explosively, so that it is possible to form a relatively thick oil film even with steel that is hardly elastically deformed. This piezo-viscous effect, that is, the positive correlation between viscosity and pressure, is a phenomenon that generally occurs in oil films under high pressure. In the elastohydrodynamic lubrication region, analysis of important phenomena of lubrication by oil films is still active today. Is underway.

  Non-Patent Document 3 states that under high pressures such as Hertz contact, lubricating oil causes glass transition or solidification, which has played an extremely important role in the operation and life of rolling bearings, traction characteristics of traction drive devices, etc. Is stated. That is, in general lubricating oil, it has been pointed out that the viscosity may rise to a solid level in the extreme pressure state, and it can be seen that the ultimate of the piezoviscous effect reaches the solid viscosity.

  The increase in pressure removes oil from the gap between the two sliding surfaces, and thins the oil film. Such liquid ultrathin films near the surface of solids are known to exhibit properties that are quite different from those of bulk liquids. Such mechanical properties of the vicinity of the solid surface or the ultra-thin liquid are mainly measured by using a surface force measuring apparatus (SFA, Surface Force Apparatus) or an atomic force microscope (AFM), and nanotribology. It gives important knowledge to the study of the essence of phenomena from the level of atoms and molecules such as nanorheology. In Non-Patent Document 4, the density of the oil-and-fat compound liquid that is structurally generally used as a lubricant is layered in a molecular aggregate in a structural manner that changes in density with respect to the distance from the solid surface. It shows the fact that the viscosity becomes very large compared to the bulk by ordering. This is different from the bulk piezoviscous effect, but when the film thickness is reduced to the nanometer order by increasing the pressure, the viscosity increases exponentially, and as a result, the same effect as the piezoviscous effect is given. .

  As a counter phenomenon of the high viscosity effect due to the molecular ordering of the ultrathin film, one of the special properties of bulk liquid is the presence of anisotropic low viscosity in the liquid crystal molecular layer in the anisotropic alignment state. It is done. In other words, Miesowics clarified the existence of anisotropy in viscosity according to the orientation direction of liquid crystal molecules at normal pressure in Non-Patent Document 5, and defined it as Miesowics viscocity. Non-Patent Document 6 proposes an active control element based on the viscosity using the difference between the electric field orientation of the liquid crystal and the shear direction, that is, the difference in anisotropic viscosity. However, this phenomenon is caused by the fact that the viscosity when sheared in the direction of the smallest diffusion cross section due to the anisotropic orientation of the molecule is the smallest. Since they are the same, there is a relative viscosity difference depending on the direction, but the tendency for the viscosity in either direction to increase with increasing pressure is the same as the piezoviscous effect for non-oriented liquids described above.

  All of the above non-patent documents are scientific phenomena that fall within the category of the piezoviscous effect, and can be summarized as a phenomenon in which an increase in pressure causes an increase in viscosity and, consequently, an increase in traction coefficient φ. As described above, in the liquid thin film under extremely severe conditions where the oil film interposed between the two sliding surfaces is subjected to extreme pressure and the film thickness decreases, the viscosity increases and the traction coefficient increases. It turns out that it is the science of natural science.

  On the other hand, Non-Patent Document 7 states that the rigidity of each part of the molecule including the ring structure of a naphthenic compound useful as a traction fluid has a positive correlation with the viscosity / pressure viscosity coefficient and the high temperature traction coefficient. ing. That is, the general rule of thumb that a relatively stiff molecule has a larger traction coefficient φ holds for naphthenic traction fluid. The rule of thumb that stiffer molecules have a larger traction coefficient is the opposite, and softer molecules lose their lubrication ability under severe conditions and lose their lubricating ability. This suggests that, in order to reach destruction, a rigid molecule must be used in practice, that is, a traction coefficient must be selected.

  Originally, the basic role of lubricants is to achieve both low friction and wear resistance, but it is also a natural science theory that achieves both low traction in extreme pressure shear fields and wear resistance due to the formation of a strong oil film. The material system that embodies it has not been clarified yet. In this way, an increase in the traction coefficient under extreme pressure conditions means that a greater load is imposed on the operation of the machine elements, and there is a strict demand for improved fuel efficiency from the viewpoints of energy saving, prevention of global warming and environmental protection. In the current situation, it must be said that it is a big scientific principle wall.

  However, the mission of the lubricant is to achieve both low traction and wear resistance in the industry. Lubrication used for all internal combustion engines such as engines, drive system parts such as manual transmissions, and machines with sliding parts such as fluid machinery. The lower the traction coefficient of the agent, the smaller the frictional resistance of the sliding part under fluid lubrication or elastohydrodynamic lubrication conditions. If the frictional resistance is small, the energy loss at the sliding part is reduced and the fuel consumption can be improved. For example, if the engine oil has low traction in an automobile, fuel efficiency is improved. That is, when driving an automobile engine, the piston ring and the cylinder liner mainly slide under fluid lubrication or elastic fluid lubrication, but if engine oil, which is a low traction fluid, is used, the frictional resistance due to the sliding is reduced, and the fuel consumption is reduced. improves. Therefore, the development of a low traction fluid is important, and the development of low traction properties under more severe extreme pressure and high temperature conditions is required.

  As described above, Patent Document 1 discloses that both low traction and wear resistance are achieved by blending a soft base oil (synthetic base oil, mineral base oil, etc.) and a viscosity index improver that compensates for the softness of the soft base oil. Although a lubricating oil composition for an internal combustion engine is provided, Patent Document 1 evaluates at a slip rate of 3%, and in this range, it is generally considered that the traction coefficient of the lubricant is small. It cannot be said that this composition is characteristic. Moreover, in the example of Patent Document 1, the latitude of the kinematic viscosity value in the refined mineral oil is narrow, and its ideal lubricating performance is quickly deteriorated due to a slight increase in kinematic viscosity due to deterioration over time or the deterioration of the viscosity index improver. This can be easily inferred from the comparative example. Therefore, it has not been shown that the combination of materials that compensate for such drawbacks can exhibit and maintain their performance in a wide temperature range and pressure range, and compensation is generally difficult. Furthermore, this is not much different from conventional lubricant compositions in that it also follows the piezoviscous effect.

  In addition, Patent Document 2 mentioned above suggests that the low traction coefficient may be caused by the molecular orientation effect, but there is no description that suggests a novel effect other than the Miesowicz viscosity. Similarly, there is no mention of a novel effect other than piezo viscosity.

  In addition, as described above, Patent Document 3 describes that the low traction fluid can obtain a low frictional resistance under both fluid lubrication and elastic fluid lubrication. The following suggests that this is a technique different from the technique of the present invention, which can obtain a characteristic low frictional resistance. Moreover, there is no description regarding the orientation of the molecule, and there is no description that suggests a novel effect other than the Miesowicz viscosity. Similarly, there is no mention of a novel effect other than piezo viscosity.

That is, it is true that the low traction fluid disclosed in the above patent document shows a low traction value in the range shown in the examples, but the theory or scientific basis for overcoming the piezoviscous effect, which is the theory of natural science. Without this, it is obvious that low traction cannot be obtained in the region where extreme pressure is applied. Current lubricants follow the piezoviscous effect, and the traction coefficient increases with extreme pressure conditions. In the current situation where fuel efficiency is strictly demanded from the viewpoint of energy saving, prevention of global warming and environmental protection, it is a big scientific principle wall. there were.
Japanese Patent Laid-Open No. 2002-3876 JP 2002-69472 A JP 2004-315703 A “Prediction of high-pressure viscosity of lubricating oil based on high-pressure density measurement” Tribologist 44 (7) pp560 (1999). “Current Status and Prospect of EHL Theory” Tribologist 49 (4) pp275 (2004). “High-pressure physical properties of lubricating oil and solid-liquid conversion lubrication under Hertzian contact” Tribologist 43 (6) pp462 (1998). “EHL of molecular order and expression of molecular effect” tribologist 49 (4) pp295 (2004). M.M. Miesowicz Nature 158,4001 (1946) pp27. “Electroviscous Effect of Liquid Crystals” Proc. 19th Leads-Lyon Symposium on tribology pp495 (1993). “Quantitative correlation between molecular structure and traction characteristics of traction fluid (second report)” Tribologist 39 (3) pp242 (1994).

The object of the present invention is not only the reactivity to the interface as in the prior art, but also has a tendency to laminate in the vicinity of the sliding surface interface, and not only steel but also a new mechanism using an organic compound having a small viscosity pressure coefficient. Another object of the present invention is to provide a lubricant composition having low friction and excellent wear resistance that enables long-term use under severe conditions even on various interfaces other than steel.
Another object of the present invention is to provide an environmentally harmonious lubricant composition against the background of a technology that enables environmentally harmful or non-use of concern elements.
Further, the present invention provides a lubricant that can be obtained in a wider range with a lower traction coefficient compared to the conventional one under a severer extreme pressure condition by combining an organic compound different from the conventionally used material and its orientation structure. It is to provide a composition.

As a result of intensive studies, the present inventor added an organic compound having a predetermined structure and a predetermined property to the current low-viscosity base oil, so that the wearability in an extremely low viscosity state at a high temperature was obtained. It was clarified from the durability test that the progress of the above can be suppressed. The use of a viscosity index improver is preferable in order to ensure further durability, but the viscosity index improver has been significantly deteriorated due to low molecular weight due to shear fracture under extreme pressure and high shear conditions. The improvement has been demanded. Surprisingly, however, it has been found that when the organic compound is added to the base oil, shear fracture of the viscosity index improver is remarkably suppressed. This is because the organic compound has orientation at the sliding surface interface, and the boundary lubricant film is formed by the same organic compound as the viscosity index improver, and these factors cause shear fracture of the viscosity index improver. I guess that it is suppressing.
Similarly, the use of an oxidation stabilizer is preferable in order to ensure the durability. However, under extreme pressure and high shear conditions, performance degradation has been remarkable due to the low molecular weight due to shear fracture, and improvement has been demanded. As a result of intensive studies by the present inventor, it has been found that the use of the organic compound in combination with the oxidation stabilizer suppresses shear fracture and extends the life.
Furthermore, even when the above organic compound is used alone, it exhibits excellent performance in terms of low friction and low wear even under extreme pressure and high shear conditions due to its orientation at the sliding surface interface and boundary lubrication film formation. I found out that I could do it.
As a result of further studies based on these findings, the present invention has been completed.

Means for solving the above-mentioned problems are as follows.
(1) A lubricant composition that is sheared by being interposed between two surfaces that move at different peripheral speeds,
(A) It has a mesogenic structure capable of forming a liquid crystal phase in its molecule, has a viscosity pressure coefficient at 40 ° C. of 20 GPa ⁻¹ or less, and develops a minimum value of a traction coefficient as the pressure increases under a pressure of 10 MPa or more. At least one organic compound having properties,
(B) a lubricating base oil, and (c) at least one viscosity index improver and / or (d) at least one antioxidant,
A lubricant composition containing
(2) (b) The lubricant composition according to (1), wherein the lubricant base oil is mineral oil and / or synthetic hydrocarbon.
(3) (b) The lubricating base oil is a poly-α-olefin or a hydride thereof, an ethylene-α-olefin copolymer or a hydride thereof, a polybutene or a hydride thereof, an alkylbenzene or an alkylnaphthalene, or an alicyclic compound. Or the lubricant composition according to (1) or (2), comprising at least one selected from the group consisting of
(4) The lubricant composition according to (1) or (2), wherein the (b) lubricant base oil is a polyether.
(5) The lubricant composition according to (1) or (2), wherein the (b) lubricating base oil comprises at least one selected from polyglycol, polyphenyl ether, alkyldiphenyl ether, or a mixture thereof.
(6) (b) The lubricant composition according to (1) or (2), wherein the lubricant base oil is an ester.
(7) (b) The lubricant composition according to (1) or (2), wherein the lubricant base oil is at least one selected from diesters, polyol esters, natural fats and oils, or mixtures thereof.
(8) (b) The lubricant composition according to (1) or (2), wherein the lubricant base oil is a phosphate ester, a polysiloxane compound, or a fluorinated polyether.
(9) (b) (1) or (2) wherein the lubricating base oil is composed of at least two mixtures selected from hydrocarbons, polyethers, esters, phosphate esters, polysiloxane compounds, and fluorinated polyethers. The lubricant composition as described.
(10) (b) The lubricant composition according to any one of (1) to (9), containing 0.1 to 10 parts by mass of an organic compound with respect to 100 parts by mass of the lubricant base oil. object.
(11) (c) The viscosity index improver is selected from the group consisting of polymethacrylate (PMA), olefin copolymer (OCP), hydrogenated styrene / diene copolymer (SDC), polyisobutylene (PIB), and mixtures thereof. The lubricant composition according to any one of (1) to (10), which is at least one selected.
(12) (d) The antioxidant is at least one selected from the group consisting of a phenol-based antioxidant, an amine-based antioxidant, a sulfur-based antioxidant, and a phosphorus-based antioxidant (1) to ( 10. The lubricant composition according to any one of 10).
(13) 0.1 to 10 parts by mass of (a) an organic compound is added to 100 parts by mass of a mixture of (b) a lubricating base oil and (c) a viscosity index improver and / or (d) an antioxidant. The lubricant composition according to any one of (1) to (12).
(14) When intervening between two surfaces moving at different peripheral speeds and being sheared, (a) the molecule of the organic compound has a molecular plane with the largest diffusion cross-section with respect to the two surfaces. The lubricant composition according to any one of (1) to (13), which can form a molecular assembly thin film oriented in parallel with each other.
(15) The lubricant composition according to any one of (1) to (14), wherein (a) the organic compound exhibits a minimum friction coefficient under a pressure of 100 MPa or more.
(16) (a) The organic compound has a plate-like or disc-like structure in the molecule as a mesogenic structure, and has a structure in which three or more terminal chains extend radially from the nucleus as a nucleus (1) to ( 15. The lubricant composition according to any one of 15).
(17) The lubricant composition according to any one of (1) to (15), wherein the organic compound has a rod-like molecular structure as a mesogenic structure.
(18) Any of (1) to (17), wherein (a) the organic compound is an organic compound having, as a mesogenic structure, at least two aromatic rings, at least one condensed ring, or a π-conjugated plane as a constituent element 2. The lubricant composition according to item 1.
(19) (a) The lubricant composition according to any one of (1) to (18), wherein the organic compound exhibits a liquid crystal phase at normal pressure.
(20) In any one of (1) to (19), (a) the organic compound does not exhibit a crystalline phase when it is sheared by being interposed between two surfaces that move at different peripheral speeds. The lubricant composition as described.
(21) (a) The lubricant composition according to any one of (1) to (20), wherein the mesogenic structure of the organic compound is represented by any one of the following general formulas [1] to [74]. .

（式中、ｎは３以上の整数を表し、＊は側鎖との結合可能部位を意味する。但し＊は３以上であれば全ての部位に側鎖が結合していなくてもよい。Ｍは金属イオン又は２つの水素原子を表す。）

(In the formula, n represents an integer of 3 or more, and * means a site capable of binding to a side chain. However, if * is 3 or more, the side chain may not be bonded to all sites.) Represents a metal ion or two hydrogen atoms.)

(22) The lubricant composition according to any one of (1) to (21), which contains two or more of the organic compounds.
(23) The lubricant composition according to any one of (1) to (22), which contains at least one organic compound that lowers a liquid crystal phase formation temperature together with the organic compound.
(24) A method for reducing friction between two surfaces by disposing the lubricant composition according to any one of (1) to (23) between two surfaces that frictionally slide at an average pressure of 10 MPa or more.
(25) The lubricant composition according to any one of (1) to (24), wherein the lubricant composition is a lubricant between two surfaces that frictionally slides at an average pressure of 10 MPa or more.

According to the present invention, the lubrication technique under the extreme pressure that has been used so far, that is, the weakness of the oil film in the low viscosity, low traction mineral oil or oil-based synthetic lubricating oil, the interface coating of polymer, sulfur, heavy metal system By replacing the conventional technology that has been supplemented by the agent with a new technology that manifests an intermolecular repulsion mechanism under extreme pressure by forming a highly ordered oriented film of a new anisotropic material under extreme pressure and shear, At the same time, extremely low traction that surpasses the low traction coefficient and tougher wear resistance can be obtained by covering the interface planarly with high order orientation. This solves all these problems at once due to the piezo-viscous effect, which is a major scientific principle wall in the current situation where fuel efficiency improvement is strictly demanded from the viewpoint of energy saving, prevention of global warming and environmental protection. The provision of new technology. According to the present invention, it is possible to provide a high-performance, environmentally friendly lubricant composition using only an organic compound without using sulfur compounds, phosphorus compounds, and heavy metals such as zinc and molybdenum, which have concerns about environmental harmful substances. The
Further, according to the present invention, not only steel but also various interfaces other than steel have a novel mechanism using an organic compound having a tendency to be laminated in the vicinity of the sliding surface interface and having a small viscosity-pressure coefficient. However, it is possible to provide a lubricant composition that has a low friction property and can be used for a long time under severe conditions and has excellent wear resistance.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
The present invention relates to a lubricant composition that is sheared by being interposed between two surfaces that move at different peripheral speeds. The lubricant composition of the present invention has (a) a mesogenic structure capable of forming a liquid crystal phase in the molecule, a viscosity pressure coefficient at 40 ° C. of 20 GPa ⁻¹ or less, and a pressure increase under a pressure of 10 MPa or more. And at least one organic compound, (b) a lubricant base oil, and (c) at least one viscosity index improver and / or (d) at least one antioxidant, which has the property of expressing the minimum value of the traction coefficient. It is a lubricant composition characterized by containing.

  The two surfaces that move at different peripheral speeds in which the lubricant composition of the present invention is used are not particularly limited, and can be used between sliding surfaces included in various machine elements. The peripheral speeds of the two surfaces are not particularly limited. If a large peripheral speed is defined as u1 (> 0) and a small peripheral speed is defined as u2, that is, | u1 |> | u2 |, the average speed (u2 + u1) / 2 is zero. The average speed of the two surfaces is usually 1000 m / s or less, preferably 1 cm / s or more and 50 m / s or less. The absolute value of the slip ratio Σ defined by 2 × (u2-u1) / (u2 + u1) is also possible to be infinitely larger than zero, but becomes -2 when u2 is zero, that is, when the machine element is stopped, -2 ≦ Although it is used in the range of Σ <0, usually there are many mechanical elements used in the range of −2 or more and −0.01 or less.

(U1-u2) / The shear rate defined by the film thickness of the lubricant composition between the two surfaces can be infinitely greater than zero, but is usually 10 ⁹ / s or less, preferably 10 / It is used at s to 10 ⁷ / s. When the lubricant composition exhibits liquid crystallinity at normal pressure, a desired high order orientation degree is maintained at a low shear rate, but in the case of non-liquid crystallinity, high order orientation by shearing is required. For example, a shear rate of 10 ⁴ / s or more may be required, but this varies depending on the structure of the organic compound contained in the lubricant composition, pressure, temperature, etc., so that an appropriate range is uniquely defined. It is difficult. The degree of orientation order of the organic compound contained in the lubricant composition is usually preferably 0.3 or more and 0.99 or less when the definition of the degree of orientation order of the liquid crystal is used. The film thickness between the two surfaces is usually 10 nm or more and 100 μm or less, preferably 50 nm or more and 5 μm or less.

It does not restrict | limit in particular about the material of the two surfaces which move, Any of steel, various metals other than steel, inorganic or organic materials other than a metal, and these mixtures may be sufficient.
Examples of metallic materials other than steel include cast iron, copper / copper-lead / aluminum alloy, castings thereof, and white metal. Organic materials include high density polyethylene (HDPE), tetrafluoroethylene resin (PFPE), polyacetal (POM), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyamideimide (PAI), polyimide (PI) And various plastics such as polypyromellitimide, polypyromellitimide, polypyromellitimide, polyamideimide, polyamideimide, polycarbonate, and polyetherimide. Examples of the inorganic material include ceramics such as silicon carbide, silicon nitride, alumina, zirconia, titanium carbide (TiC), zirconia carbide (ZrC), and titanium nitride (TiN); and carbon materials. Examples of these mixtures include organic-inorganic composite materials in which fibers such as glass, carbon, or aramid are combined in plastic, and ceramic and metal composite material cermets.

  Also, as steel, structural structural alloy steel such as carbon steel for mechanical structure, nickel chrome steel, nickel chrome molybdenum steel, chrome steel, chrome molybdenum steel, aluminum chrome molybdenum steel; steel such as stainless steel and multi-aged steel; Is mentioned. At least a part of these surfaces may be coated with a film made of a metal material other than steel, or an organic or inorganic material other than the metal material. Coating films include gas-phase coating methods such as diamond-like carbon thin films, such as thin films by chemical vapor deposition or physical vapor deposition, thin films by liquid phase coating methods such as plating, thin films by powder coating or thermal spraying, and organic or inorganic Examples thereof include a porous membrane.

Also, a porous sintered layer is formed on at least one of the two surfaces, and the porous layer is impregnated with a lubricant composition, and the lubricant composition is appropriately supplied to the sliding surface during sliding. You may comprise. The porous layer may be made of any of a metal material, an organic material, and an inorganic material. Specifically, sintered ceramics, porous ceramics formed by strongly bonding fine particles of calcium zirconate (CaZrO ₃ ) and magnesia (MgO), silica and boric acid components are thermally phase separated. Porous glass, ultra-high molecular weight polyethylene powder sintered porous molding, fluororesin-based porous membrane such as ethylene tetrafluoride, polysulfone-based porous membrane used for microfilters, etc. Examples thereof include a porous film formed by causing phase separation during polymerization of a poor solvent and its molded body forming monomer.

Examples of the metal or metal oxide sintered layer include a porous layer formed by sintering a copper-based, iron-based, or TiO ₂ -based powder. The copper-based metal sintered layer is formed by compressing and forming a mixture of copper powder (for example, 88% by mass), tin (for example, 10% by mass) and graphite (for example, 2% by mass) on a cast iron substrate at 250 MPa. Can be formed by sintering in a reducing stream at a high temperature, for example, about 770 ° C. for about one hour. In addition, the iron-based metal sintered layer is compression-molded at 250 MPa by placing a mixture of iron powder with copper powder (eg, 3% by mass) and chemical carbon (0.6% by mass) on a cast iron substrate. Can be formed by sintering in a reducing gas stream at a high temperature, for example, about 770 ° C. for about one hour. The TiO ₂ sintered layer is made of a mixture of Ti (OC ₈ H ₁₇ -n) (for example, 33% by mass), fine powder of TiO ₂ (for example, 57% by mass) and PEO (molecular weight MW = 3000), It is formed by installing on cast iron and heating and sintering at 560 ° C. for 3 hours while irradiating with UV light.

  Regarding the average pressure between two surfaces, the organic compound usually becomes incompressible under a pressure of about 100 MPa, the effect of “mass action” on the chemical reaction becomes less important, and the pressure overcomes the steric hindrance of the organic compound. That there are examples of reaction. E. WEALE "High-pressure chemical reaction" Baifukan (1969) p1. It is described in.

(A) Predetermined organic compound The lubricant composition of the present invention has a mesogenic structure capable of forming a liquid crystal phase in the molecule, a viscosity pressure coefficient at 40 ° C. of 20 GPa ⁻¹ or less, and a pressure of 10 MPa or more. And at least one organic compound having the property of expressing the minimum value of the traction coefficient as the pressure increases.
The (a) organic compound develops a lower traction coefficient as the pressure increases under a pressure of 10 MPa or more, and develops a minimum value of the traction coefficient. Furthermore, it is preferable to develop a minimum traction coefficient under a pressure of 100 MPa or more. The organic compound (a) preferably expresses a low traction coefficient of 0.07 or less, and more preferably expresses a low traction coefficient of 0.05 or less. It has been found that under the pressure in the region of 10 MPa or more, the influence of elastic strain starts to appear on the interface of glass and steel. Therefore, on the two surfaces where the lubricant composition of the present invention is used, the main motion is preferably performed under a pressure of 10 MPa or more, more preferably performed at a pressure of 50 MPa or more, and under a pressure of 100 MPa or more. More preferably it is performed. In addition, it is thought that the said lubricant composition reaches a mixed lubrication area | region with a pressure rise, and the film | membrane interface is destroyed. Therefore, the reduction in the traction coefficient of the lubricant composition is accompanied by a pressure increase in a range of 10 MPa or more and a pressure equal to or lower than a pressure that becomes a mixed lubrication region.

Here, the traction coefficient is a dimensionless amount obtained by dividing a tangential force generated when slippage occurs in rolling by a normal force (vertical load), that is, a sliding friction coefficient. “Tribology” by Yamamoto and Kaneda, published by Science and Engineering (1998) p. 1
29. As shown in Fig. 5.18, when the slip rate is small, the traction coefficient increases proportionally and then becomes a constant value. When the slip rate further increases, the traction coefficient gradually decreases due to the effect of frictional heat. I know what to show. Therefore, in order to compare the traction coefficients, the temperature should be kept constant and the comparison should be made in a relatively large slip ratio region where the maximum traction coefficient can be obtained.

The organic compound (a) has a viscosity pressure coefficient at 40 ° C. of 20 GPa ⁻¹ or less, and develops a lower traction coefficient as the pressure increases under a pressure of 10 MPa or more. Here, the viscosity pressure coefficient can be calculated by the method described in Tribologist, Vol. 38, No. 10, pp927 (1993). The lubricant composition of the present invention preferably has a viscosity pressure coefficient at 40 ° C. of 13 GPa ⁻¹ .
However, in the case of a compound that is solid at 40 ° C., the viscosity pressure coefficient is obtained at two or more temperatures exhibiting a liquid under the measurement conditions, and these values are defined as a value of 40 ° C. obtained by extrapolating to the low temperature side.

  The (a) organic compound has a mesogenic structure in the molecule. Here, the mesogenic structure is also called an intermediate phase (= liquid crystal phase) forming molecule (Liquid Crystal Dictionary, Japan Society for the Promotion of Science, 142nd Committee on Organic Materials for Information Science, edited by Liquid Crystal Division, 1989). It is almost synonymous with structure. Specifically, typical mesogens having a rod-like structure exhibiting a nematic phase and a smectic phase include an azomethine group, a phenylazo group, a phenylazoxy group, a benzoate group, a biphenyl group, a terphenyl group, and a cyclohexylcarboxylate group. , Phenylcyclohexane group, biphenylcyclohexane group, pyrimidine group, dioxane group, cyclohexylcyclohexane ester group, cyclohexylethyl group, tolan group, 2,3-difluorophenylene group, alkenyl group, cyclohexyl group, or a composite or linked group thereof It is done. Those exhibiting a cholesteric phase include cholesterol derivative esters. In flat and disc-like structures exhibiting discotic nematic and columnar phases, hexasubstituted benzene, 1,3,5-triazine, hexaarylethynylbenzene, 2,3,6,7,10,11-hexasubstituted Triphenylene, 2,3,7,8,12,13-hexasubstituted truxene, hexasubstituted trioxatruxene, 1,2,3,5,6,7-hexasubstituted anthraquinone, octasubstituted phthalocyanine or porphyrin, hexasubstituted macro Examples include cyclen, bis (1,3-diketone) copper complex, tetraarylbipyranylidene, tetrathiafulvalene, and inositol.

  The molecules of the organic compound are preferably oriented with the molecular plane having the largest diffusion cross section oriented parallel to the shear plane when sheared between the two planes. In the case of a rod-like molecule, it is necessary to form a molecular assembly thin film in an orientation state in which its inertial axis or optical axis is parallel to the shear plane. In the case of flat and discotic structural compounds, it is necessary to form a molecular assembly thin film in an orientation state in which the widest molecular plane is parallel to the shear plane.

  From the viewpoint of the traction coefficient, in general, the latter gives a smaller traction coefficient for organic compounds having a rod-like structure and organic compounds having a plate-like structure and a disk-like structure. The reason for this is presumed that the latter has a relatively large area that contributes to the adsorptivity to the interface and the repulsion between adjacent molecules. Further, in order to efficiently maintain the flatness and intermolecular repulsion, organic compounds having a plate-like structure and a disk-like structure having a condensed ring by a π bond as a constituent element are preferable. However, as the number of condensed rings increases, the crystallization temperature also increases, the viscosity increases relatively, and it tends to be difficult to use near room temperature. Should not be large.

The flat and discotic structural compounds refer to compounds having a flat or discotic molecular part in the mother nucleus. The plate-like or disc-like morphological characteristics of the mother nucleus part excluding the side chain part can be expressed, for example, as follows for the hydrogen substitution product that is the original compound. First, the molecular size is determined as follows.
1) Construct a molecular structure that is as close to a plane as possible, preferably a planar molecular structure. In this case, as the bond distance and bond angle, it is preferable to use standard values according to the orbital mixture. For example, the Chemical Society of Japan, Chemical Handbook 4th Edition, Chapter II, Volume 15 (1993 published by Maruzen) You can refer to it.
2) Using the structure obtained in 1) as an initial value, the structure is optimized by a molecular orbital method or a molecular force field method. Examples of the method include Gaussian 98, MOPAC2000, CHARMm / QUANTA, and MM3, and Gaussian 98 is preferable.
3) The center of gravity of the structure obtained by structure optimization is moved to the origin, and the coordinate axis is taken as the inertial principal axis (the principal axis of the inertia tensor ellipsoid).
4) A sphere defined by the van der Waals radius is given to each atom, thereby describing the shape of the molecule.
5) Measure the length in the direction of each coordinate axis on the van der Waals surface, and let them be a, b and c, respectively.
When a disk-like form is defined using a, b, and c obtained by the above procedure, c ≦ b <a and a / 2 ≦ b ≦ a, preferably c ≦ b <a and 0.7a ≦ b. ≦ a can be expressed. Moreover, it is preferable that b / 2> c.

  As specific compounds, for example, the Chemical Society of Japan, Quarterly Chemical Review No. 22 “Chemicals of Liquid Crystals”, Chapter 5 and Chapter 10 Section 2 (published in 1994). Destrade et al., Mol. Cryst. Liq. Cryst. 71, 111 (1981), B.R. Kohne et al., Angew. Chem. 96, 70 (1984), J. Am. M.M. Lehn et al. Chem. Soc. Chem. Commun. , 1794 (1985), J. Am. Zhang, J. et al. S. A study report by Moore et al. Am. Chem. Soc. 116, 2655 (1994), and derivatives of the mother nucleus compound. For example, benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives, porphyrin derivatives, anthracene derivatives, azacrown derivatives, cyclohexane derivatives, heterocyclic derivatives, β-diketone metal complex derivatives, hexaethynylbenzene derivatives, dibenzopyrene derivatives, coronene derivatives And phenylacetylene macrocycle derivatives. Furthermore, the cyclic compounds described in the Chemical Society of Japan, “Chemical Review No. 15 New Aromatic Chemistry” (published by the University of Tokyo Press, 1977) and their electronic structures such as heteroatom substitution can be mentioned. In addition, as in the case of the metal complex, a plurality of molecules may be formed by a hydrogen bond, a coordinate bond, or the like to form a disk-like molecule. A discotic liquid crystal compound is formed with a structure in which these are used as the mother nucleus at the center of the molecule, and linear or branched alkyl groups, alkoxy groups, alkoxycarbonyl groups, substituted benzoyloxy groups, and the like are radially substituted as side chains. .

  Preferable examples of the mother nucleus at the center of the molecule of the plate-like and discotic structure compounds include structures represented by any of the following general formulas [1] to [74]. Note that n represents an integer of 3 or more, and * means a site capable of binding to a side chain. However, as long as * is 3 or more, the side chain may not be bonded to all sites. M represents a metal ion or two hydrogen atoms. M represents a metal ion or two hydrogen atoms, that is, [5] and [6] may or may not contain a central metal.

  The mother nucleus preferably has a π-conjugated skeleton containing a polar element. In the above, [1], [2], [3], [4], [5], [6], [9 ], [11], [12], [17], [20], [21], [23], [24], [28], [29], [30], [36], [38], [42], [46], [56], [58], [67], [68], [73], [74] are preferable, and [1], [2], [3], [6] among them are preferable. ], [11], [12], [21], [23], [30], [46], [58], [68], [73] are preferred, and particularly preferably, they can be obtained synthetically and inexpensively. It is a benzene ring of [1] or a 1,3,5-tris (arylamino) -2,4,6-triazine ring of [2].

  Examples of the side chain include an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkylthio group, and an acyloxy group. The side chain may contain an aryl group or a heterocyclic group. In addition, C.I. Hansch, A.M. Leo, R.A. W. It may be substituted with a substituent described in Taft, Chemical Review (Chem. Rev.), 1991, Vol. 91, pages 165 to 195 (American Chemical Society). Representative examples include an alkoxy group and an alkyl group. , An alkoxycarbonyl group, and a halogen atom. Furthermore, the side chain may have a functional group such as an ether group, an ester group, a carbonyl group, a cyano group, a thioether group, a sulfoxide group, a sulfonyl group, or an amide group.

More specifically, examples of the side chain moiety include alkanoyloxy groups (eg, hexanoyloxy, heptanoyloxy, octanoyloxy, nonanoyloxy, decanoyloxy, undecanoyloxy), alkylsulfonyl groups (eg, hexyl). Sulfonyl, heptylsulfonyl, octylsulfonyl, nonylsulfonyl, decylsulfonyl, undecylsulfonyl), alkylthio groups (eg, hexylthio, heptylthio, dodecylthio), alkoxy groups (eg, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, Nonyloxy, decyloxy, undecyloxy), 2- (4-alkylphenyl) ethynyl groups (eg, methyl, ethyl, propyl, butyl, pentyl, hexyl as alkyl groups) , Heptyl, octyl, nonyl), terminal ruoxy, 7-vinylheptyloxy, 8-vinyloctyloxy, 9-vinylnonyloxy), 4-alkoxyphenyl groups (for example, those mentioned above as alkoxy groups as alkoxy groups) , An alkoxymethyl group (for example, those mentioned as the alkoxy group described above as an alkoxy group), an alkylthiomethyl group (for example, those mentioned as the alkylthio group described above as an alkylthio group), 2-alkylthiomethyl (eg as an alkylthio group, as described above) In the above-mentioned alkylthio group), 2-alkylthioethoxymethyl (for example, the above-mentioned alkylthio group as an alkylthio group), 2-alkoxyethoxymer group (for example, the above-mentioned alkoxy group as an alkoxy group) ), 2-alkoxy A sulfonylethyl group such as the alkoxy group mentioned above as an alkoxy group), cholesteryloxycarbonyl, β-sitosteryloxycarbonyl, 4-alkoxyphenoxycarbonyl group (eg an alkoxy group mentioned above as an alkoxy group) , 4-alkoxybenzoyloxy group (for example, the above-mentioned alkoxy group as an alkoxy group), 4-alkylbenzoyloxy group (for example, the above-mentioned 2- (4-alkylphenyl) ethynyl group as an alkyl group) ), 4-alkoxybenzoyl groups (for example, those mentioned as the alkoxy group described above as the alkoxy group). Of the above-mentioned compounds, the phenyl group may be another aryl group (for example, naphthyl group, phenanthryl group, anthracene group), or may be further substituted in addition to the above-described substituents. The phenyl group is a heteroaromatic ring (for example, pyridyl group, pyrimidyl group, triazinyl group, thienyl group, furyl group, pyrrolyl group, pyrazolyl group, imidazolyl group, triazolyl group, thiazolyl group, imidazolyl group, oxazolyl group, thiadialyl group. Oxadiazolyl group, quinolyl group, isoquinolyl group).
The number of carbon atoms contained in one side chain is preferably 1 or more and 30 or less, and more preferably 1 or more and 20 or less.

The discotic compound is preferably a compound having a cyclic group having a discotic partial structure and a plurality (preferably 2 to 11) side chains bonded to the cyclic group. At least one of the side chains preferably has an ester bond. In particular, at least one of the side chains preferably contains a group represented by the following general formula (4a) or general formula (4b). In the following formula, the left side (-X ⁰ ) is bonded to the D side.

In the formula, X ⁰ is a single bond, an NR ¹ group (R ¹ is a hydrogen atom or an alkyl group having 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a combination thereof. Represents a linking group.
L ⁰ represents an alkylene group (preferably a linear, branched or cyclic alkylene group having 1 to 20 carbon atoms), an NR ¹ group (R ¹ is a hydrogen atom or a carbon number of 1 to 30). An alkyl group), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a combination thereof. The divalent linking group may have a substituent. L ⁰ is preferably an alkylene group.
In addition, the group of the combination of X ⁰ and L ⁰ is preferably —O (C═O) -alkylene- or —O (C═O) -cycloalkylene-.
R ⁰ is located at the end of the side chain of the compound and represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group.

Moreover, it is more preferable that at least one of the side chains includes a group represented by the general formula (4a). Among these, it is more preferable that the side chain contains a group represented by the following general formula (4). In the following formula, the left side (-L ⁰¹ ) is bonded to the cyclic base side.

L ⁰¹ is synonymous with X ⁰ . L ⁰¹ is preferably an oxygen atom, a sulfur atom,-(C = O) O-, -NH- (C = O) O-. R ⁰¹ represents a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and p and q each represents an integer. R ⁰¹ preferably has 1 to 40 carbon atoms, and more preferably 1 to 20 carbon atoms. Substituents include halogen atoms, alkoxy groups (methoxy, ethoxy, methoxyethoxy, phenoxy, etc.), sulfide groups (methylthio, ethylthio, propylthio, etc.), alkylamino groups (methylamino, propylamino, etc.), acyl groups (acetyl, Propanoyl, octanoyl, benzoyl, etc.) and acyloxy groups (acetoxy, pivaloyloxy, banzoyloxy, etc.), aryl groups, heterocyclic groups, hydroxyl groups, mercapto groups, amino groups, cyano groups, nitro groups, carboxyl groups, sulfo groups, carbamoyl groups Group, sulfamoyl group, ureido group and the like. p is preferably from 1 to 20, and more preferably from 2 to 10. q is preferably 1 to 10, and more preferably 1 to 5.

  Moreover, it is also preferable that at least one of the side chains includes a group represented by the following general formula (5) or (6).

In the formula, R ⁰¹ represents a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, m and n each represent an integer, and represent a group having the same meaning as R ⁰¹ in formula (4).

In the formula, R ²⁵ represents a substituent, and a24 represents an integer of 1 to 5.

  Moreover, it is also preferable that at least a part of the side chain is a group represented by the following general formula (7).

In the formula, L ²¹ is a single bond, an NR ¹ group (R ¹ is a hydrogen atom or an alkyl group having 1 to 30 carbon atoms), an alkylene group, an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a combination thereof. Represents a divalent linking group consisting of An oxygen atom, an oxyalkylene group, an oxycarbonyl group, an aminocarbonyl group, a carbonyloxy group, and a carbonyl group are preferable, and an oxycarbonyl group and a carbonyl group are more preferable.

In the above formula, examples of the substituents R ²⁵ , R ⁷¹ and R ⁷² include a halogen atom (for example, fluorine, chlorine, bromine), an alkyl group (an alkyl group having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms). For example, methyl, ethyl, propyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl), an alkenyl group (an alkenyl group having 2 to 40 carbon atoms, preferably 2 to 20 carbon atoms) For example, vinyl, 2-buten-1-yl, oleyl), alkynyl group (2 to 40 carbon atoms, preferably 2 to 20 alkynyl group such as propargyl), aryl group (6 to 40 carbon atoms) Of 6 to 20 aryl groups such as phenyl and naphthyl, and heterocyclic groups (having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms). Terocyclic groups such as 2-furyl, 2-thienyl, 4-pyridyl, 2-imidazolyl, 2-benzothiazolyl, 2-benzoxazolyl, 1-benzimidazolyl), cyano group, hydroxyl group, nitro group, carboxyl group An alkoxy group (an alkoxy group having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms such as methoxy, ethoxy, hexyloxy, octyloxy, 2-ethylhexyloxy, decyloxy, dodecyloxy, tetradecyloxy, hexadecyl) Oxy, octadecyloxy), aryloxy groups (C6-C40, preferably 6-20 aryloxy groups such as phenoxy, 1-naphthoxy), silyloxy groups (C3-C40, preferably Is a silyloxy group of 3 to 20, for example, trimethyl Luoxy), heterooxy groups (heterooxy groups having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms, such as 2-furyloxy, 2-tetrahydropyranyloxy, 3-pyridyloxy, 2-imidazolyloxy), acyloxy Group (acyloxy group having 2 to 40 carbon atoms, preferably 2 to 20 carbon atoms, for example, acetoxy, butanoyloxy, octanoyloxy, dodecanoyloxy, benzoyloxy), carbamoyloxy group (1 to 40 carbon atoms) Preferably a carbamoyloxy group of 1 to 20, for example, N, N-diethylcarbamoyloxy), an alkoxycarbonyloxy group (a C2-C40, preferably 2 to 20 alkoxycarbonyloxy group, for example, , Ethoxycarbonyloxy, butoxycarbonyloxy, -Ethylhexyloxycarbonyloxy, dodecyloxycarbonyloxy, hexadecyloxycarbonyloxy), aryloxycarbonyloxy groups (aryloxycarbonyloxy groups having 7 to 40 carbon atoms, preferably 7 to 20 carbon atoms, for example phenoxy Carbonyloxy), amino groups (amino groups having 0 to 40 carbon atoms, preferably 1 to 20 carbon atoms, such as amino, N-methylamino, N-2-ethylhexylamino, N-tetradecylamino, N, N -Diethylamino, N, N-dioctylamino), acylamino group (acylamino group having 1 to 40 carbon atoms, preferably 1-20, for example, acetylamino, octanoylamino, dodecanoylamino), aminocarbonylamino group (C1-C40, preferably 1 20 aminocarbonylamino groups such as N, N-dioctylcarbamoylamino), alkoxycarbonylamino groups (2 to 40 carbon atoms, preferably 2 to 20 alkoxycarbonylamino groups such as methoxycarbonylamino, Ethoxycarbonylamino, 2-ethylhexylcarbonylamino, tetradecyloxycarbonylamino), aryloxycarbonylamino group (aryloxycarbonylamino group having 7 to 40 carbon atoms, preferably 7 to 20 carbon atoms, for example, phenoxycarbonylamino) A sulfamoylamino group (a sulfamoylamino group having 0 to 40 carbon atoms, preferably 0 to 20 carbon atoms, such as N, N-dimethylsulfamoylamino), alkyl and arylsulfonylamino groups (carbon atoms) Number 1 0, preferably 1-20 alkyl and arylsulfonylamino groups such as methylsulfonylamino, butylsulfonylamino, dodecylsulfonylamino, p-toluenesulfonylamino), mercapto groups, alkylthio groups (1-40 carbon atoms) Preferably an alkylthio group of 1 to 20, for example, methylthio, ethylthio, 2-ethylhexylthio, dodecylthio), an arylthio group (having 6 to 40, preferably 6 to 20 arylthio groups, for example, phenylthio ), A heterocyclic thio group (a heterocyclic thio group having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms such as 4-pyridylthio, thiazol-2-ylthio, benzoxazol-2-ylthio, 1-phenyltetrazole -5-ylthio, 1,3,4-thia Azol-2-ylthio), a sulfamoyl group (a sulfamoyl group having 0 to 40 carbon atoms, preferably 0 to 20 carbon atoms, such as sulfamoyl, N, N-diethylsulfamoyl, N-hexadecylsulfamoyl), Sulfo group, alkyl and arylsulfinyl group (C1-C40, preferably 1-20 alkyl and arylsulfinyl groups such as methylsulfinyl, phenylsulfinyl), alkyl and arylsulfonyl groups (C1-C1 40, preferably 1-20 alkyl and arylsulfonyl groups, for example, methylsulfonyl, butylsulfonyl, hexadecylsulfonyl, p-tolylsulfonyl), acyl groups (1-40 carbon atoms, preferably 1-20) An acyl group of, for example, acetyl , Propionyl, isobutyryl, tetradecanoyl, benzoyl), an aryloxycarbonyl group (an aryloxycarbonyl group having 7 to 40 carbon atoms, preferably 7 to 20 carbon atoms, for example, phonoxycarbonyl), an alkoxycarbonyl group (carbon atom) An alkoxycarbonyl group having 2 to 40, preferably 2 to 20, for example, ethoxycarbonyl, t-butoxycarbonyl, hexadecyloxycarbonyl), carbamoyl group (having 1 to 40, preferably 1 to 20 carbon atoms) A carbamoyl group, for example a carbamoyl, N, N-diethylcarbamoyl, N-dodecylcarbamoyl), aryl and heterocyclic azo group (an aryl and heterocyclic azo group having 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms, For example, phenylazo, 3-methyl-1 2,4-oxadiazol-5-ylazo, 2-methylthio-1,3,4-thiadiazol-5-ylazo), an imide group (4-40 carbon atoms, preferably 4-20 imide groups, For example, succinimide, phthalimide), phosphino group (phosphino group having 0 to 40 carbon atoms, preferably 0 to 20 carbon atoms), phosphinyl group (phosphinyl group having 0 to 40 carbon atoms, preferably 0 to 20 carbon atoms), phosphine group Finyloxy group (0 to 40 carbon atoms, preferably 0 to 20 phosphinyloxy group), phosphinylamino group (0 to 40 carbon atoms, preferably 0 to 20 phosphinylamino group) Group) and a silyl group (a silyl group having 3 to 40 carbon atoms, preferably 3 to 20 carbon atoms, for example, trimethylsilyl, t-butyldimethylsilyl). Furthermore, the substituents R ⁷¹ and R ⁷² also include those substituents substituted with one or more substituents selected from these substituents. As the substituent for R ⁷¹ , an alkoxy group, an alkoxycarbonyl group and an acyl group substituted with a substituent containing a linear or branched alkyl residue are preferable. a is 0 or an integer of 1 to 5, preferably 1 to 3.
R ⁷¹ preferably has 1 to 40 carbon atoms, more preferably 1 to 20 carbon atoms.

  Moreover, it is also preferable that at least one of the m side chains (R—X—) includes a partially fluorocarbon group and a fluorocarbon group. That is, it is also preferable that at least one of the general formulas (4a), (4b), (4), (5), (6) and (7) contains a partially fluorinated carbon group and a fluorinated carbon group. . The presence or absence of a double bond, a branch, a cyclic group, or an aromatic ring may be used for the fluorocarbon group.

  Here, for liquid crystallinity, linearity, flatness and rigidity, which are three-dimensional factors, and anisotropy of polarizability, which are electrostatic factors, are important. The structure of almost all liquid crystal compounds can be schematically represented by a rigid core structure and flexible side chains. The mesogenic structure is a coined term of a structure in which an intermediate phase (mesophase) is induced (generated), and refers to the former rigid core structure portion. A liquid crystalline compound is a thermotropic liquid crystal that exhibits a thermodynamically stable liquid crystal phase at a specific temperature and pressure range, and a lyotropic liquid crystal that exhibits a liquid crystal phase at a specific temperature, pressure, and concentration range in a solvent. And classified. However, even a compound having a mesogenic structure and a flexible side chain does not necessarily exhibit liquid crystallinity. Therefore, the organic compound used in the lubricant composition of the present invention must have a mesogenic structure in the molecule, but need not be a liquid crystal compound.

  The rigid repulsive force due to this rigid planar structure of organic compounds is an important factor for the expression of liquid crystallinity, but the space in which flexible side chains that exist simultaneously behave freely, that is, the free volume is large, In particular, it has been found that the lubricant composition that has been used so far provides characteristics that are not present. That is, a liquid crystal compound, more preferably a compound having a disk-like mesogenic structure, has several flexible side chains around a ring having a rigid planar structure, so that the free volume of these side chains becomes relatively large. It is expected that the free volume can be secured even under a situation where pressure is applied and the free volume is compressed. Therefore, the rate of increase in viscosity with respect to pressure is relatively small, and exhibits a small viscosity pressure coefficient equivalent to that of animal and vegetable fats and oils. Therefore, even under high pressure, it exhibits a low viscosity coefficient in the shear direction, and planar molecules exhibit a high viscosity coefficient due to high adsorption force and orientation (lamination) properties in the interface direction, so-called isotropic oily compounds so far It is estimated that both low viscosity and wear resistance under extreme pressure that could not be achieved in

  The lubricant composition of the present invention is characterized by giving a low traction coefficient particularly under extreme pressure conditions, that is, in the elastohydrodynamic lubrication region. Therefore, in the so-called fluid lubrication region in the normal pressure region, the viscosity of an organic compound having a wide π conjugate plane with high flatness is generally relatively large. Accordingly, it can be said that the liquid crystallinity in this region, that is, normal pressure, can exhibit the low viscosity of Myesovitz due to shearing, and is more advantageous. Therefore, in order to develop a low traction coefficient in as wide a temperature range as possible, it is preferable to use an organic compound that exhibits a liquid crystal phase at normal pressure. Further, the liquid crystal temperature range at normal pressure is as wide as possible and has a low viscosity plate shape or It is more preferable to use an organic compound having a disk-like structure. In that respect, organic compounds that can form a liquid crystal phase in a wide temperature range by linking two or more disc-shaped mesogenic structures such as triarylmelamine rings, hexa- and pentaarylethynylbenzenes, and triphenylene rings. Is also preferable. On the other hand, it is known that the organic compound exhibits a very high traction coefficient at the crystal phase temperature when it is subjected to shearing between two surfaces. On the other hand, when it does not form a clear crystalline phase and exhibits an amorphous state (amorphous state), or when the rate of forming a crystalline phase is slow, it becomes supercooled and apparently exhibits an amorphous state (amorphous state) In general, a small traction coefficient is maintained in the case, and therefore, it is considered preferable that a crystalline phase is not exhibited when shearing is interposed between two surfaces.

  Specific examples of the organic compound (a) are given below, but the present invention is not limited by the following specific examples.

  The lubricant composition of the present invention may contain two or more organic compounds having a mesogenic structure in the molecule. In such a case, two or more kinds of compounds having different mesogen structures may be included, and a plurality of types of organic compounds having the same mesogenic structure and having different side chains substituted may be used. Moreover, the said lubricant composition may contain the organic compound which reduces the liquid crystal phase formation temperature with the said organic compound. As a combination of such compounds at normal pressure, non-patent literature Mol. Cryst. Liq. Cryst. , 1981, Vol. 71, pp111. FIG. To FIG. And the compounds described in Japanese Patent Application Laid-Open No. 9-104866. As described in the references, there are few descriptions regarding the combination of such compounds, but there is no chemical structure particularly excluded or restricted structurally, and as a structure that lowers the liquid crystal phase formation temperature more efficiently. , Having a structure similar to the side chain of the liquid crystal compound used, preferably a compound containing at least one polar functional group such as an ether group or a carbonyl group, such as an ether containing an oligoethyleneoxy group and an alkyl group having 6 or more carbon atoms The following specific compound examples, such as a compound and an ester compound, are mentioned.

(B) Lubricating oil base oil The lubricant composition of the present invention further contains (b) a lubricating oil base oil. Any of the current lubricating base oils can be used. For current lubricant base oils, see Tribology Handbook C, Chapter 1 Lubricant 1.1.1 Base oil p. 579-589 First Edition 2001 Edit: Japan Society of Tribologists Publication: Corporation
It is described in detail in Yokendo, which is a mineral oil base oil obtained by refining heavy fractions obtained from crude oil distillation refining by solvent extraction or hydrotreating, and a synthetic oil system that uses chemical synthesis as the main production process. Broadly divided into base oils. Mineral oil base oils are (1) classified into paraffinic, naphthenic, and aromatic based on the structural classification of the main component hydrocarbons, but most of them are the former except for special base oils. In addition to paraffinic and naphthenic and monocyclic, bicyclic and polycyclic aromatic hydrocarbons, sulfur fractions such as sulfide and thiophene, nitrogen compounds such as quinoline and carbazole, Resin, etc. are included, and it is not always easy to control basic performance as a base oil such as high oil viscosity index, low temperature fluidity, sludge solubility, flash point, oxidation stability, etc. Therefore, a synthetic base oil has been demanded. As the synthetic base oil, (2-1) Hydrocarbon base oil (a) Polyolefin: Poly-α-olefin (α-olefin (1-decene) as a raw material produced by polymerization reaction and hydrogenation treatment ( PAO), polybutene which is a copolymer of n-butene mainly composed of isobutylene, and a copolymer of ethylene and α-olefin (OCP), etc., b) alkyl aromatics: alkylbenzenes and alkylnaphthalenes C) alicyclic compound system: having a naphthene ring, characterized by a high viscosity pressure coefficient (high traction coefficient), and mainly used for hydrocarbon base oil of traction oil), (2-2) Polyether base oil (Polyglycol type, which is a polymer of ethylene oxide and propylene oxide), and phenyl ether type having 3-5 aromatic rings. (2-3) Ester base oils: (Diesters synthesized from dibasic acids and monohydric alcohols, synthesized from polyhydric alcohols and monocarboxylic acids) (2-4) Phosphorus compound base oils (all phosphate ester compounds, triaryl or trialkyl phosphate ester base oils) , Characterized by flame retardancy), (2-5) silicon compound base oil (silicone oil which is a polymer compound having a Si—C bond and a Si—O—Si bond is common), and (2-6) Halogen compound base oils (fluorinated polyethers of perfluorinated polyglycol type base oils (abbreviated as PFPE or PFPAE) base oils are chemically stable).

  In the present invention, as the (b) lubricating base oil, either mineral oil or synthetic oil can be used, or a mixture thereof may be used. Synthetic oils are preferred, and synthetic hydrocarbon oils are more preferred. Among them, poly-α-olefin or hydride thereof, ethylene-α-olefin copolymer or hydride thereof, mixture of poly-α-olefin or hydride thereof and alkylnaphthalene, and ethylene-α-olefin copolymer Alternatively, when at least one selected from a mixture of the hydride and alkylnaphthalene is used, the compatibility with the organic compound (a) is good, which is also preferable from the viewpoint of durability.

  The poly α-olefin hydride (hereinafter referred to as PAO) that can be used in the present invention is not particularly limited, and various types can be used. Usually, PAO having an average molecular weight of 200 to 1600 is preferable, and PAO having 400 to 800 is more preferable. Such a PAO can be obtained by hydrogenating a polymer obtained by polymerizing decene-1, isobutene or the like with a Lewis acid complex or an aluminum oxide catalyst. By using PAO as the base oil, the heat resistance can be improved, and the amount of sludge generated from the oil can be extremely suppressed, so that a lubricant composition with a longer life can be obtained.

  The ethylene-α-olefin copolymer hydride (hereinafter referred to as PEAO) that can be used in the present invention is not particularly limited, and various types can be used. As PEAO, for example, a polymer obtained by hydrogenating a polymer obtained by polymerizing ethylene and an α-olefin such as 1-decene or isobutene with a Lewis acid catalyst or the like can be used. The number average molecular weight of PEAO is usually preferably 200 to 4000, more preferably 1000 to 2000.

  Any alkylnaphthalene that can be used in the present invention can be used without particular limitation as long as it has one or more alkyl groups on the naphthalene ring. Preferably, it is mono-, di- or trialkylnaphthalene having a total carbon number of the alkyl group of about 5 to 25, and more preferably has both a lower alkyl group and a higher alkyl group. Examples of the lower alkyl group include a methyl group, an ethyl group, a propyl group, and an isopropyl group, and a methyl group is particularly preferable. The higher alkyl group is not particularly limited, and may be a linear alkyl group or a branched alkyl group, but preferably has a linear alkyl group having excellent viscosity index and lubricity. Examples of such an alkylnaphthalene include dialkylnaphthalene having a methyl group and a secondary alkyl group having 10 to 24 carbon atoms on the naphthalene ring, or a mixture thereof as described in JP-A-8-302371. It is done. In practice, known ones, particularly those that are commercially available, are advantageous in terms of availability.

  (B) Lubricating oil base oil used in the present invention is preferably a mixture of PAO and PEAO and alkylnaphthalene, the blending ratio of the former being 0.1 to 50% by weight, preferably 2 to 40% by weight, and the latter Is 50 to 99.9% by mass, preferably 60 to 98% by mass. When the blending ratio of PAO and PEAO is less than 0.1% by mass, the heat resistance cannot be improved, and when it exceeds 50% by mass, the ratio of alkylnaphthalene in the base oil is decreased, and the oil film formation rate is decreased.

  In the lubricant composition of the present invention, it is preferable to contain 0.01 to 30 parts by mass of (a) an organic compound with respect to 100 parts by mass of the (b) lubricant base oil, and 0.1 to 10 parts by mass is contained. It is more preferable to contain 0.5 to 5 parts by mass. This range is preferable from the viewpoint of long-term durability with a low friction coefficient and cost performance.

(C) Viscosity index improver The lubricant composition of the present invention contains (c) a viscosity index improver and / or (d) an antioxidant. First, (c) the viscosity index improver will be described. Various conventionally known viscosity index improvers can be used in the present invention.
In recent years, the momentum for protecting the global environment has increased, and the fuel efficiency of industrial machines and automobiles has been further demanded. In order to improve the fuel efficiency, it is practically desirable that the frictional resistance of the driving part is reduced, especially the characteristics relating to the viscosity of the lubricating oil, that is, the viscosity does not change as much as possible over a wide range from low temperature to high temperature. As this scale, a viscosity index (VI) is used, and the greater the viscosity index, the higher the stability against temperature change. It is known that the viscosity index can be improved by adding certain polymers (viscosity index improvers) to the base oil and / or lubricating oil. The reason why the temperature dependence of the viscosity of the lubricating oil is reduced by the addition of the viscosity index improver is considered as follows. That is, at low temperatures (usually 40 ° C.), the viscosity index improver hardly dissolves in low-viscosity oils, and the viscosity of the oil does not increase, but at high temperatures (usually 100 ° C.) The oil solubility of the oil is improved and the viscosity of the whole oil increases due to the thickening effect.
Such a polymer is called a viscosity index improver, and can be used as the (c) viscosity index improver in the present invention. Examples of the viscosity index improver include polymethacrylate (PMA) (more specifically, PMA described in JP-A-7-62372), olefin copolymer (OCP) (more specifically, Japanese Examined Patent Publication 46- No. 34508), hydrogenated styrene / diene copolymer (SDC) (more specifically, SDC described in Japanese Patent Publication No. 48-39203), polyisobutylene (PIB), and the like. Examples of the viscosity index improver comprising SDC include a random copolymer, a block copolymer (for example, a random copolymer described in JP-A-49-47401) and a star polymer (for example, a special polymer). No. 52-96695 has been developed, and any of these can be used in the present invention. Each lubricating oil to which these polymers are added has its characteristics. That is, PMA is excellent in improving the viscosity index and has a pour point lowering effect, but is inferior in the thickening effect. In order to improve the thickening effect, the molecular weight may be increased. However, in this case, the stability against the shearing force accompanying the stirring of the lubricating oil is extremely deteriorated. PIB has a large thickening effect but is inferior in viscosity index improvement. OCP and SDC have a large thickening effect and low viscosity at low temperatures, but their viscosity index improvement is inferior to PMA. Also, PMA can easily impart clean dispersion performance to disperse sludge in lubricating oil by copolymerizing polar monomers as compared to other types (see Japanese Patent Publication No. 51-20273). . Currently, multi-grade oils with excellent viscosity index improving performance are generally used as lubricating oils. Recently, higher performance viscosity index improvers have been desired due to demands for improving fuel consumption. As a composition that satisfies this requirement, it is conceivable to use a mixture of PMA and OCP or SDC. However, since the compatibility is poor if these are simply mixed, the lubricating oil is separated into two phases. Therefore, in order to prevent this separation, graft copolymers of two different types of polymers have been proposed (specifically, graphs described in JP-B-4-50328 and JP-A-6-346078). Of course, such a graft copolymer can also be used as (c) viscosity index improver.

  On the other hand, such a viscosity index improver is required to have shear stability as well as performance to improve the viscosity index. As used herein, “shear stability” means the rate of decrease in viscosity after shear is applied to the viscosity before shear is applied. Therefore, good shear breaking stability means that the rate of decrease in viscosity after applying shear is small. Since automobile engine oil is a drive system lubricant, the viscosity index improver added to the oil is subjected to a strong shearing force (or physical shearing stress) by the crankshaft and gears. Due to this shear stress, the polyalkyl (meth) acrylate, which is the base polymer of the viscosity index improver, is oriented in the shear direction (that is, aligned and stretched), the polymer chain is broken, and the molecular weight of the polymer may be reduced. As a result, the viscosity index tends to decrease. This tendency becomes stronger as the molecular weight increases. Therefore, in order to improve the shear stability, it is necessary to lower the weight average molecular weight of the viscosity index improver. However, when the weight average molecular weight of the viscosity index improver is lowered, it is necessary to increase the amount of the viscosity index improver added to the lubricating oil in order to sufficiently improve the viscosity index. In order to solve the problems related to the fundamental principle, a polymerization method of a vinyl monomer (see JP 2002-12883 A), optimization of an olefin copolymer composition (see JP 2003-48931 A), a base oil, A technique for optimizing the alkyl methacrylate composition (see Japanese Patent Application Laid-Open Nos. 2004-307551 and 2004-149794) has been proposed, and it is disclosed that low temperature fluidity can be ensured at the same time. Of course, a viscosity index improver improved by this technique can also be used in the present invention. JP-A-2001-234186 discloses anti-shudder ability by optimizing the alkyl methacrylate composition, JP-A-6-17077 discloses anti-oxidation ability by containing alkylphenol, and JP-A-2002-3873. The publication discloses that a polyalkylene thioether can be contained to impart coking resistance. In the present invention, these highly functional agents may be used as the (c) viscosity index improver.

(D) Antioxidant Next, (d) antioxidant usable in the present invention will be described. The antioxidant is one selected from the group consisting of phenolic and amine antioxidants that act as free radical chain reaction terminators, sulfur antioxidants and phosphorus antioxidants that act as peroxide decomposers. Alternatively, two or more kinds of antioxidants can be used alone or as a mixture, but it is preferable to use an amine and a phenol in combination.
Examples of phenolic antioxidants include 2,6-di-t-butylphenol, 4,4′-methylenebis (2,6-di-t-butylphenol), and 2,6-di-t-butyl-4- Ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate], 4,4 '-Butylidene-bis- (6-tert-butyl-3-methylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Examples include phenol. From the viewpoint of evaporation characteristics, 4,4′-methylenebis (2,6-di-t-butylphenol) is preferable.

Examples of amine antioxidants include di (p-octylphenyl) amine, di (p-nonylphenyl) amine, phenyl-α-naphthylamine, octylphenyl-α-naphthylamine and nonylphenyl-α-naphthylamine, Examples include phenothiazine, and dioctyl diphenylamine and phenothiazine are preferable.
Examples of sulfur-based antioxidants include sulfurized fats and oils, dibenzyl sulfite, and dicetyl sulfide.
Examples of the phosphorus antioxidant include zinc dialkyldithiophosphate and zinc diallyldithiophosphate.

  A metal deactivator can be blended as an agent that acts to prevent oxidation indirectly. Typical examples of the metal deactivator include benzotriazole and its derivatives, but also imidazoline and pyridine derivatives. Many of these compounds are effective among compounds having at least an N-CN bond, and have an action of forming an inert film on a metal surface and an antioxidant action. Other than these, there are compounds having an N—C—S bond, but benzotriazole derivatives and the like are effective due to volatility and the like.

  In the lubricant composition of the present invention, 0.1 part of (a) an organic compound is added to 100 parts by weight of a mixture of (b) a lubricant base oil and (c) a viscosity index improver and / or (d) an antioxidant. You may mix | blend -10 mass parts. Further, (b) the lubricating base oil contains 50 to 99.9% by mass of alkylnaphthalene and 50 to 0.1% by mass of hydrogenated poly α-olefin or ethylene-α-olefin copolymer. A lubricant composition containing 0.1 to 10 parts by mass of (a) an organic compound with respect to 50 to 1 part by mass of (c) viscosity index improver and / or (d) antioxidant is preferred.

  The lubricant composition of the present invention has various other additives, that is, antiwear agents, extreme pressure agents, detergent dispersants, metal deactivators, corrosion inhibitors, in order to ensure practical performance adapted to various applications. An agent, a rust inhibitor, an antifoaming agent, and the like can be appropriately added within a range not impairing the object of the present invention. However, also when it contains another component, it is preferable that the 1 type (s) or 2 or more types of said organic compound is 50 mol% or more in a whole composition, and it is more preferable that it is 80 mol% or more.

  The mechanical element in which the lubricant composition of the present invention is used is not particularly limited in its structure as long as it has two surfaces that move at different peripheral speeds. It may be any mechanical element incorporated in a conventionally known friction sliding portion that requires lubricating oil, grease, or the like. The two surfaces that move at different peripheral speeds may be curved surfaces, flat surfaces, or may have uneven portions on all or part of the surfaces. For example, a sliding bearing, a friction sliding part of a rolling bearing, etc. are mentioned. The mechanical element of the present invention may further include a gear, a cam, a screw, and a traction drive as a transmission element. Moreover, you may provide contact type seals, such as an oil seal, a mechanical seal, and a piston ring, as a sealing element for sealing the said lubricant composition.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

[Examples 1 to 30]
A lubricant composition was prepared by blending (a) a predetermined organic compound and (d) an antioxidant with the lubricant base oil. About these lubricant compositions, the friction coefficient and the acid value were measured, respectively. Next, as an evaluation of the lubricant composition, a friction coefficient and an acid value after a heating test of 165.5 ° C. × 1300 rotations × 36 hours were measured according to JISK2415.
The friction coefficient measurement test was carried out using a SRV measurement tester with line contact, load 200 N, temperature 80 ° C., measurement time 15 minutes, amplitude 1 mm, and cycle 50 Hz. Moreover, an acid value is shown as an oleic acid content by titration. However, in the case of deterioration determination, the magnitude of infrared carboxylic acid absorption or this is shown in terms of oleic acid content.
The results are shown in Table 1.

[Comparative Examples 1 to 10]
Lubricant compositions not blended with (a) a predetermined organic compound or (d) an antioxidant were prepared and evaluated in the same manner as in the examples. The results are shown in Table 2.

[Examples 31 to 60]
Lubricant compositions were prepared by blending (a) a predetermined organic compound and (c) a viscosity index improver with the lubricant base oil.
The friction coefficient was measured for these lubricant compositions. The friction coefficient measurement test was performed using a SRV measurement tester at a line contact, a load of 200 N, a temperature of 100 ° C., a measurement time of 15 minutes, an amplitude of 1 mm, and a cycle of 50 Hz.
Moreover, about these lubricant compositions, shear stability was evaluated from the viscosity loss rate (calculated by the following formula) by ultrasonic irradiation based on JPS-5S-29-88. A smaller value is preferable.
Viscosity reduction rate (%) = ((Vo−Vf) / Vo) × 100
Vo: Kinematic viscosity before ultrasonic irradiation (cSt)
Vf: Kinematic viscosity after ultrasonic irradiation (cSt)
The results are shown in Table 3.

[Comparative Examples 11 to 20]
A lubricant composition not containing (a) a predetermined organic compound or (c) a viscosity index improver was prepared and evaluated in the same manner as in the examples. The results are shown in Table 4.

From the results of Tables 1 to 4, the lubricant compositions of Comparative Examples 1 to 10 had different friction coefficients before and after the heating test, while the lubricant compositions of Examples 1 to 30 of the present invention were It was found that there was almost no change in the coefficient of friction before and after the heating test, and the durability was high.
Further, from the results of Tables 5 to 8, the lubricant compositions of Examples 31 to 60 of the present invention are superior in shear stability and friction as compared with the lubricant compositions of Comparative Examples 11 to 20. It was also confirmed that there was an effect of reducing the coefficient. The above results indicate that (a) the lubricant composition of the present invention containing a predetermined organic compound is excellent in fuel economy and has a long life.

Claims (21)

A lubricant composition that is sheared by being interposed between two surfaces that move at different peripheral speeds,
(A) at least one kind having a mesogen structure in the molecule, a viscosity pressure coefficient at 40 ° C. of 20 GPa ⁻¹ or less, and a property of expressing a minimum value of a traction coefficient with a pressure increase under a pressure of 10 MPa or more. Organic compounds,
(B) a lubricating base oil, and (c) at least one viscosity index improver and / or (d) at least one antioxidant,
A lubricant composition containing (B) The lubricant composition according to claim 1, wherein the lubricant base oil is a mineral oil and / or a synthetic hydrocarbon. (B) The lubricating base oil is a poly-α-olefin or a hydride thereof, an ethylene-α-olefin copolymer or a hydride thereof, a polybutene or a hydride thereof, an alkylbenzene or an alkylnaphthalene, an alicyclic compound, or The lubricant composition according to claim 1 or 2, comprising at least one selected from a mixture of the above. (B) The lubricant composition according to claim 1 or 2, wherein the lubricant base oil is a polyether. The lubricant composition according to claim 1 or 2, wherein the (b) lubricating base oil comprises at least one selected from polyglycol, polyphenyl ether, alkyldiphenyl ether, or a mixture thereof. (B) The lubricant composition according to claim 1 or 2, wherein the lubricant base oil is an ester. (B) The lubricant composition according to claim 1 or 2, wherein the lubricating base oil comprises at least one selected from diesters, polyol esters, natural fats and oils, or mixtures thereof. (B) The lubricant composition according to claim 1 or 2, wherein the lubricant base oil is a phosphate ester, a polysiloxane compound, or a fluorinated polyether. The lubricant composition according to claim 1 or 2, wherein the (b) lubricant base oil is composed of at least two mixtures selected from hydrocarbons, polyethers, esters, phosphate esters, polysiloxane compounds, and fluorinated polyethers. object. (B) The lubricant composition according to any one of claims 1 to 9, comprising 0.1 to 10 parts by mass of an organic compound with respect to 100 parts by mass of the lubricant base oil. (C) The viscosity index improver is at least selected from the group consisting of polymethacrylate (PMA), olefin copolymer (OCP), hydrogenated styrene / diene copolymer (SDC), polyisobutylene (PIB) and mixtures thereof. It is 1 type, The lubricant composition of any one of Claims 1-10. (D) The antioxidant is at least one selected from the group consisting of a phenol-based antioxidant, an amine-based antioxidant, a sulfur-based antioxidant, and a phosphorus-based antioxidant. 2. The lubricant composition according to item 1. Claims obtained by blending 0.1 to 10 parts by mass of (a) an organic compound with 100 parts by mass of a mixture of (b) a lubricating base oil and (c) a viscosity index improver and / or (d) an antioxidant. Item 13. The lubricant composition according to any one of Items 1 to 12. When shearing by intervening between two surfaces moving at different peripheral speeds, (a) the molecule of the organic compound has a molecular surface with the largest diffusion cross-section parallel to the two surfaces. 14. The lubricant composition according to any one of claims 1 to 13, which can form an oriented molecular assembly thin film. The lubricant composition according to any one of claims 1 to 14, wherein (a) the organic compound exhibits a minimum friction coefficient under a pressure of 100 MPa or more. (A) The organic compound has a flat or disk-like structure in the molecule as a mesogenic structure, and has a structure in which three or more terminal chains extend radially from the nucleus. 2. The lubricant composition according to item 1. (A) The lubricant composition according to any one of claims 1 to 15, wherein the organic compound has a rod-like molecular structure as a mesogenic structure. The organic compound (a) is an organic compound having, as a mesogenic structure, at least two aromatic rings, at least one condensed ring, or a π-conjugated plane as a constituent element. Lubricant composition. The lubricant composition according to any one of claims 1 to 18, wherein (a) the organic compound exhibits a liquid crystal phase at normal pressure. The lubricant composition according to any one of claims 1 to 19, wherein (a) the organic compound does not exhibit a crystalline phase when it is sheared by being interposed between two surfaces that move at different peripheral speeds. object. (A) The lubricant composition according to any one of claims 1 to 20, wherein the mesogenic structure of the organic compound is represented by any one of the following general formulas [1] to [74].

(In the formula, n represents an integer of 3 or more, and * means a site capable of binding to a side chain. However, if * is 3 or more, the side chain may not be bonded to all sites.) Represents a metal ion or two hydrogen atoms.)